In recent years, as a technique for improving a transmission rate in a radio communication system, there have been studied MIMO (Multi Input Multi Output) communication, communication using STC (Space Time Coding), and the like, in which a transmission apparatus is provided with a plurality of transmission antennas so as to transmit different signals with the same frequency from the individual transmission antennas.
These techniques have in common that multiple transmission antennas are arranged in the transmission apparatus and no effect can be obtained unless the respective transmission antennas are apart from one another by more than a predetermined distance. That is, for example in MIMO communication, multiple transmission antennas are arranged apart from each other by more than a predetermined distance to reduce fading correlation between the transmission antennas and the reception antenna, so that the reception apparatus can separate the signals transmitted from the individual transmission antennas. Accordingly, as compared with a case in which communication is performed using one transmission antenna, radio communication can be performed at high transmission rate in proportion to increase in the number of transmission antennas.
Moreover, similarly, in a case where multicarrier modulation such as OFDM (Orthogonal Frequency Division Multiplex) and the like is applied to the aforementioned MIMO communication and STC communication, the respective transmission antennas are arranged apart from each other by more than a predetermined distance, so that the carrier signals transmitted from the individual transmission antennas are affected by frequency selective fading in different patterns to reduce fading correlation between the transmission antenna and the reception antenna for each carrier. Accordingly, the reception apparatus can separate the signals transmitted from the individual transmission antennas and radio communication can be performed at high transmission rate in proportion to increase in the number of transmission antennas as compared with the case in which communication is performed using one transmission antenna.
However, there has been a continuing trend of miniaturization with mobile station apparatuses such as cellular phones and the like used in radio communication system, and there is a problem that separate arrangement of a plurality of transmission antennas has a certain limit. Accordingly, there is a case in which fading correlation between the transmission antenna and the reception antenna increases, so that desired transmission rate cannot be attained even if MIMO communication and STC communication are performed.